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Wire communications in telephones
Write the first paragraph of your page here. 'TELEPHONE-LANDLINE' This type of telephone refers to a phone which works through a solid medium telephone line such as a metal wire or a fibre optic cable. This is the main difference with cell phones because this one uses radio waves for tranmission. A fixed phone line is a line which is not a mobile phone line.A fixed phone line can be hard-wired or cordless. Fixed wireless refers to those operations in fixed places such as home. These devices derive their electricity power from the mains electricity utility.This is another difference with mobile wireless that are battery-powered -An optical fibre is a transparent fibre glass-made and thicker than a hair that functions as a waveguide. -Landline is a term also used to describe a connection between 2 or more points that has a dedicated physical cable, as opposed an always available-private link that is implemented like a circuit in a wired-switched system. It can be also called homephone, land-line or main line. -A cordless telephone is used to replace a handset cord with a radio link.Section heading HOW DOES THE TELEPHONE WORKS? The first phones were made by microphones and speakers joined by cable, which did not allow communication with other terminals. A new technical advance, which is called switched network, allowed later the massive impact of the telephone. The switched network is a connection system in which each terminal is connected to a telephone exchange, and each exchange is connected to other telephone exchanges. This means, that the terminals are not directly connected to each other, so the telephone exchange communicates different terminals. When you call someone, a way between the two terminals involved is establish, in a process called circuit switching. In the first years of the telephone, circuit switching was done manually. The person who initiated the call, took down his phone and indicated to an operator who he wanted to speak. This operator was responsible for connecting the cables. Today circuit switching is done automatically. Each person has a number. In the marking process, this number is transmitted to the telephone exchange with different frequency tones. A computer has to process this information and make the connections. Telephony is a communication system in which the transmitter and the receiver are connected by cables. This is called transmission system with wires. The most common wire systems are electrical circuits. The wires are normally made of copper with insulated lining. There are three types of cables: 1 - Pair cables: They are the most common in indoor telephone installations. They are two separate copper wires with plastic lining. 2 - Twisted Pair Cables: They are like the pair cables, but they are intertwined to avoid interferences. They are mainly used in computer networks. 3 - Coaxial cables: They consist of two concentric conductors separated by an insulated material. They are used in the antenna connections and televisions. The telephone is formed by microphones and speakers. To convert the sounds into electromagnetic waves that can be processed and transmitted by electronic means we use microphones and for the reverse transformation, we use speakers. Microphones and speakers are considered transducers. There are different types of microphones. The work of one of the microphones is to transfer a current of electricity through a capsule filled with compressed charcoal granules by a plate called diaphragm that vibrates when it touches the sound wave. The electric voltage varies according to the sound wave produced by the vibration. There are also different types of speakers. The most common works on an electromagnet located between permanent magnets. The electrical signal passes through the electromagnet and makes vibrate a membrane to which is connected. The membrane pushes the air molecules that surrounds it and generates the sound.